To Create a Free Curve
Free curves can lie anywhere in three-dimensional space.
1. Click 
Style > 
Set Active Plane to set the active datum plane. The points that you define for the curve lie on this plane by default.
Style > Set Active Plane to set the active datum plane. The points that you define for the curve lie on this plane by default.2. Click Style > 
Curve. The Curve tab opens.
Style > Curve. The Curve tab opens.3. To create a free curve, click Free Curve.
Free Curve.4. Define points for the curve.
You can create Style curves using control points as well as interpolation points.
5. To define the curve using control points, click 
Control Points.
Control Points.6. To set the curve degree, type or select a value in the Degree box.
7. Closed curves are created as periodic. To change the closed curve to nonperiodic, click 
Periodic Curve. Click Periodic Curve again to change the curve back to periodic.
Periodic Curve. Click Periodic Curve again to change the curve back to periodic. | For periodic curves, the value for the curve degree must be an odd number. When a curve of an even-numbered degree is changed to periodic, the degree increases by one. |
8. To create a curve that is symmetric:
a. Click 
Symmetrical Curve.
Symmetrical Curve.b. Click the Plane collector, and then select a datum plane to define the symmetry plane for the curve.
c. If required, to reverse the curve direction, right-click the curve and choose Flip Curve Direction.
9. To maintain the curve shape during edits by moving the free points in proportion to the soft points, click the Options tab, and select the Proportional Update check box.
| | A curve without proportional update only changes shape at the soft point during edits. |
10. Click 
OK.
OK.